Agriculture a major cause of air pollution

Food cultivation is the dominant source of fine particulate matter (PM2.5) in ambient air in Europe, the central US and parts of China, according to a new study from the Earth Institute at Columbia University.

Agricultural air pollution comes mainly in the form of ammonia (NH3), which enters the air as a gas from heavily fertilized fields and livestock waste. It blows in over cities, reacts with emissions of oxides of nitrogen (NOx) and sulphur (SO2) from traffic and industry, and leads to the formation of so-called secondary particles. The combination of intensive agriculture, traffic and industry is unfortunately quite typical for some of the most populated parts of North America, Europe and Asia, which means that these particles are formed where they can cause a lot of damage.

The researchers used a global model to study the origin of fine particulate matter in different regions of the world. They divided the emission sources into three categories: natural, anthropogenic non-agricultural and agricultural. Agricultural emissions were defined as the change that occurred if all agricultural activities were turned on and off.

In Europe, emission precursors from fertilizers and livestock were responsible for 55 per cent of the anthropogenic PM2.5. In the US, agricultural emissions represented around half of the human caused emissions. China shows the highest level of agriculture-related PM in absolute figures, and slightly less than half of the anthropogenic PM pollution. India is the only region in the study where agricultural emissions are less significant for PM2.5 levels in ambient air.